In 1964, coagulation or gel formation of horseshoe crab, amoebocyte lysate (hereinafter may be abbreviated LAL), with a very small amount of an intracellular toxin of Gram negative bacteria (hereinafter abbreviated as endotoxin (Et) or lipopolysaccharide (LPS)) was discovered, and multiple factors, serine protease precursors, including Et (LPS) sensitive factor (factor C), participating in the gel formation have been found. This reaction is composed of a cascade mechanism which resembles to the coagulation system of blood of mammals, and similar mechanisms have also been reported in the other invertebrates
LAL has been known to react with a very small amount of (1.fwdarw.3)-.beta.-D-glucan (hereinafter abbreviated as .beta.-glucan) to cause gel formation in addition to Et, and a sensitive factor G which recognizes .beta.-glucan has been found. An induction of gel formation as well as Et by a quite different coagulation cascade route (factor G system) from a route by way of factor C (factor C system) has been elucidated. Further, .beta.-glucan is a constructive polysaccharide of fungal cell wall and this route is presumed to be closely related to a defense system of a living body as well as factor C system, Heretofore, .beta.-glucan binding protein such as blood coagulating factor G of horseshoe crab (FEBS Lett., 129, 318-321 (1981)), .beta.-glucan recognizing protein of silkworm (prophenol oxidase) (J. Biol. Chem., 263, 12056-12062 (1988)), .beta.-glucan receptor of human monocytes (J. Exp. Med., 173, 1511-1520 (1991)), an adjuvant receptor accompanied with localized opsonin formation (J. Immunol., 124, 3307-3315 (1985)), .beta.-glucan elicitor to plant cells (J. Cell Biol., 78, 627 (1978)), a glucan binding protein derived from Streptococcus sobrinus (Infect Immun., 60 (12) 5291-5293 (1992)) and .beta.-glucan specific lectin derived from great wax moth (Galleria mellonella L., (Matha V., 64, 35-42 (1990)) have been reported.